But it may be doubted whether the mere enunciation of the doctrine, even in this precise and definite form, has of itself been sufficient to secure this end.  There is good reason to believe that the doctrine would not have been safe from challenge if it had not been safeguarded by the supremacy of the British Fleet.  For throughout the last half-century all the world has known that any defiance of this doctrine, and any attack upon America, would bring Britain into the field.  During all this period one of the factors of world-politics has been the existence of an informal and one-sided alliance between Britain and America.  The alliance has been informal, because it has not rested upon any treaty or even upon any definite understanding.  It has been one-sided, because while average opinion in America has been distrustful of Britain, has been apt to put unfavourable constructions upon British policy, and has generally failed to appreciate the value and significance of the work which Britain has done in the outer world, Britain, on the other hand, has always known that America stood for justice and freedom; and therefore, however difficult the relations between the two powers might occasionally become, Britain has steadfastly refused to consider the possibility of a breach with America, and with rare exceptions has steadily given her support to American policy.  The action of the British squadron off the Philippines in 1898, in quietly interposing itself between the threatening German guns and the American Fleet, has, in fact, been broadly typical of the British attitude.  This factor has not only helped to preserve the Monroe Doctrine from challenge, it has indirectly contributed to deepen the American conviction that it was possible, even in the changed conditions of the modern world, to maintain a complete isolation from the political controversies of the powers.

During the period 1815-1878, then, while the greater part of Europe was still indifferent to extra-European affairs, America had developed into a vast state wherein freedom and law were enthroned, a huge melting-pot wherein diverse peoples were being gradually unified and turned into a new nation under the moulding power of a great tradition of liberty.  But her geographical position, and certain elements in her tradition, had hitherto led her to abstain from, and even to repudiate, that great part in the shaping of the common destinies of civilisation to which she was manifestly called by her wealth, her numbers, her freedom, and her share in the traditions of all the European peoples.  In the nature of things, whatever some Americans might think, this voluntary isolation could not continue for ever.  It was to be brought to an end by the fevered developments of the next era, and by the great challenge to the liberties of the world in which it culminated.

VI

THE TRANSFORMATION OF THE BRITISH EMPIRE, 1815-1878